Home About us Contact
|
Home About us Contact | ||
|
|
||
Multiple Days (multiple + day)
Selected AbstractsEconomic Production Lot Sizing with Periodic Costs and Overtime,DECISION SCIENCES, Issue 3 2001E. Powell Robinson Jr Abstract Traditional approaches for modeling economic production lot-sizing problems assume that a single, fixed equipment setup cost is incurred each time a product is run, regardless of the quantity manufactured. This permits multiple days of production from one production setup. In this paper, we extend the model to consider additional fixed charges, such as cleanup or inspection costs, that are associated with each time period's production. This manufacturing cost structure is common in the food, chemical, and pharmaceutical industries, where process equipment must be sanitized between item changeovers and at the end of each day's production. We propose two mathematical problem formulations and optimization algorithms. The models' unique features include regular time production constraints, a fixed charge for each time period's production, and the availability of overtime production capacity. Experimental results indicate the conditions under which our algorithms' performance is superior to traditional approaches. We also test the procedures on a set of lot-sizing problems facing a national food processor and document their potential economic benefit. [source] Do ,9 -tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users?ADDICTION, Issue 12 2009Erin L. Karschner ABSTRACT Aims To quantify blood ,9 -tetrahydrocannabinol (THC) concentrations in chronic cannabis users over 7 days of continuous monitored abstinence. Participants Twenty-five frequent, long-term cannabis users resided on a secure clinical research unit at the US National Institute on Drug Abuse under continuous medical surveillance to prevent cannabis self-administration. Measurements Whole blood cannabinoid concentrations were determined by two-dimensional gas chromatography-mass spectrometry. Findings Nine chronic users (36%) had no measurable THC during 7 days of cannabis abstinence; 16 had at least one positive THC ,0.25 ng/ml, but not necessarily on the first day. On day 7, 6 full days after entering the unit, six participants still displayed detectable THC concentrations [mean ± standard deviation (SD), 0.3 ± 0.7 ng/ml] and all 25 had measurable carboxy-metabolite (6.2 ± 8.8 ng/ml). The highest observed THC concentrations on admission (day 1) and day 7 were 7.0 and 3.0 ng/ml, respectively. Interestingly, five participants, all female, had THC-positive whole blood specimens over all 7 days. Body mass index did not correlate with time until the last THC-positive specimen (n = 16; r = ,0.2; P = 0.445). Conclusions Substantial whole blood THC concentrations persist multiple days after drug discontinuation in heavy chronic cannabis users. It is currently unknown whether neurocognitive impairment occurs with low blood THC concentrations, and whether return to normal performance, as documented previously following extended cannabis abstinence, is accompanied by the removal of residual THC in brain. These findings also may impact on the implementation of per se limits in driving under the influence of drugs legislation. [source] The Pharmacokinetics of Antiepileptic Drugs in Rats: Consequences for Maintaining Effective Drug Levels during Prolonged Drug Administration in Rat Models of EpilepsyEPILEPSIA, Issue 7 2007Wolfgang Löscher Summary:, Rodent models of chronic epilepsy with spontaneous recurrent seizures likely represent the closest parallel to the human condition. Such models may be best suited for therapy discovery for pharmacoresistant epilepsy and for antiepileptogenic or disease-modifying therapeutics. However, the use of such rodent models for therapy discovery creates problems with regard to maintaining effective drug levels throughout a prolonged testing period. This is particularly due to the fact that rodents such as rats and mice eliminate most drugs much more rapidly than humans. Thus, knowledge about elimination rate of a test drug in a laboratory species is essential for development of a treatment paradigm that allows maintaining adequate drug levels in the system over the period of treatment. Currently, the most popular models of epilepsy with spontaneous seizures are poststatus epilepticus models of temporal lobe epilepsy in rats. Such models are both used for studies on antiepileptogenesis and drug resistance. For validation of these models, current antiepileptic drugs (AEDs) have to be used. In this article, the elimination rates of these AEDs and their effective plasma levels in rats are reviewed as a guide for developing treatment protocols for chronic drug testing. The advantages and disadvantages of several technologies for drug delivery are discussed, and some examples for calculation of adequate treatment protocols are given. As shown in this review, because of the rapid elimination of most AEDs in rats, it is no trivial task to maintain effective steady-state AED levels in the plasma throughout the day over multiple days to ensure that there will be adequate levels in the system for the purpose of the experiment. However, the use of an adequate dosing regimen that is based on elimination rate is an absolute prerequisite when using rat models for discovery of new antiepileptogenic therapies or therapies for pharmacoresistant epilepsy, because otherwise such models may lead to erroneous conclusions about drug efficacy. [source] On the reliability of a dental OSCE, using SEM: effect of different daysEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 3 2008M. Schoonheim-Klein Abstract Aim:, The first aim was to study the reliability of a dental objective structured clinical examination (OSCE) administered over multiple days, and the second was to assess the number of test stations required for a sufficiently reliable decision in three score interpretation perspectives of a dental OSCE administered over multiple days. Materials and methods:, In four OSCE administrations, 463 students of the year 2005 and 2006 took the summative OSCE after a dental course in comprehensive dentistry. The OSCE had 16,18 5-min stations (scores 1,10), and was administered per OSCE on four different days of 1 week. ANOVA was used to test for examinee performance variation across days. Generalizability theory was used for reliability analyses. Reliability was studied from three interpretation perspectives: for relative (norm) decisions, for absolute (domain) and pass,fail (mastery) decisions. As an indicator of reproducibility of test scores in this dental OSCE, the standard error of measurement (SEM) was used. The benchmark of SEM was set at <0.51. This is corresponding to a 95% confidence interval (CI) of <1 on the original scoring scale that ranged from 1 to 10. Results:, The mean weighted total OSCE score was 7.14 on a 10-point scale. With the pass,fail score set at 6.2 for the four OSCE, 90% of the 463 students passed. There was no significant increase in scores over the different days the OSCE was administered. ,Wished' variance owing to students was 6.3%. Variance owing to interaction between student and stations and residual error was 66.3%, more than two times larger than variance owing to stations' difficulty (27.4%). The SEM norm was 0.42 with a CI of ±0.83 and the SEM domain was 0.50, with a CI of ±0.98. In order to make reliable relative decisions (SEM <0.51), the use of minimal 12 stations is necessary, and for reliable absolute and pass,fail decisions, the use of minimal 17 stations is necessary in this dental OSCE. Conclusions:, It appeared reliable, when testing large numbers of students, to administer the OSCE on different days. In order to make reliable decisions for this dental OSCE, minimum 17 stations are needed. Clearly, wide sampling of stations is at the heart of obtaining reliable scores in OSCE, also in dental education. [source] Characterization and Variability of Endotoxin and 3-Hydroxy Fatty Acids in an Office Building During a Particle Intervention StudyINDOOR AIR, Issue 1 2000Cynthia J. Hines Abstract Air and dust samples were collected on two floors of an office building during a double-blind particle intervention study to examine spatial and temporal variability of airborne endotoxin over a period of weeks, and to characterize endotoxin activity and lipopolysaccharide (LPS) content in carpet and chair dust. Air samples were collected on multiple days within and across weeks. Dust samples were collected from carpets and chairs one day per week for three weeks. Endotoxin was measured using a Limulus assay. Dust samples were analyzed for LPS by determination of 3-hydroxy fatty acids (3-OHFAs) using gas chromatography-mass spectrometry. The geometric mean (geometric standard deviation) for 96 indoor air samples was 0.24 (1.6) EU/m3. Significant within-floor spatial variation of airborne endotoxin was found (P<0.0001, n=80). Temporal variability of airborne endotoxin was not significant across weeks. Mean (±SD) endotoxin levels in carpet dust (59±9.3 EU/mg dust, n=12) and in chair dust (38±7.7 EU/mg dust, n=10) were significantly different (P<0.001). Carbon chain length-dependent differences in 3-OHFA levels by dust source and floor were found. Enhanced air filtration did not significantly affect airborne endotoxin (P=0.62); however, total dust mass and total endotoxin in carpet dust samples increased significantly after enhanced surface cleaning (P<0.01). These findings suggest that spatial variability, dust source, and surface cleaning may influence building occupant exposures to endotoxin., [source] A Bayesian hierarchical distributed lag model for estimating the time course of risk of hospitalization associated with particulate matter air pollutionJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2009Roger D. Peng Summary., Time series studies have provided strong evidence of an association between increased levels of ambient air pollution and increased hospitalizations, typically at a single lag of 0, 1 or 2 days after an air pollution episode. Two important scientific objectives are to understand better how the risk of hospitalization that is associated with a given day's air pollution increase is distributed over multiple days in the future and to estimate the cumulative short-term health effect of an air pollution episode over the same multiday period. We propose a Bayesian hierarchical distributed lag model that integrates information from national health and air pollution databases with prior beliefs of the time course of risk of hospitalization after an air pollution episode. This model is applied to air pollution and health data on 6.3 million enrollees of the US Medicare system living in 94 counties covering the years 1999,2002. We obtain estimates of the distributed lag functions relating fine particulate matter pollution to hospitalizations for both ischaemic heart disease and acute exacerbation of chronic obstructive pulmonary disease, and we use our model to explore regional variation in the health risks across the USA. [source] Detection of Mollicutes in bioreactor samples by real-time transcription-mediated amplificationLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010S. Laborde Abstract Aim:, Contamination by Mollicutes is a significant challenge for research laboratories and biopharmaceutical industry. It leads to alteration of results or production quality as well as loss of time, materials and revenue. These organisms can czoriginate from mammalian, avian, insect, plant or fish cells. Culture-based methods may require 28 days to detect Mollicutes. Traditional microbiology could advantageously be replaced by nucleic acid testing for earlier detection. Methods and Results:, A membrane filtration-based concentration of the Mollicutes has been coupled to real-time transcription-mediated amplification (real-time TMA) to demonstrate these advantages. The eight species required by European Pharmacopoeia have been tested and were detected with sensitivity below 100 CFU per 20-ml sample. Co-culture experiments, in which Mollicutes are grown with CHO-S (suspension) or HEK 293 (adherent) cells, were also performed to respectively mimic a bioreactor or flask contamination. Despite the fact that Mollicutes can attach to or invade mammalian cells, they were consistently detected over multiple days. Conclusions:, the sample preparation and amplification method used in this study increases sensitivity and reduces time-to-result for detection of Mollicutes. Significance and Impact of the Study:, the described system allows real-time monitoring for microbial contamination of cell-based processes and products for the biopharmaceutical industry. [source] | ||||||||||